Clavisangemon
Successfully complete the Undead Yard quest with Veemon or the Item Road quest with Dorumon.

Agumon
Reach level 16 with Guilmon.

Duplicate Items, Bits, etc.
First off, you need to have at least 1 bit or item. This works well if you've picked up a weapon in the begining of the game with many mod slots, which can be sold for alot of bits. Next, you need to load up your game and log-in with that Digimon, but don't start the game. Instead, jack in another controller(taking your current controller out and putting it in another controller slot works), and create a new Digimon. Now start game, and give the items or the amount of bits you want to duplicate to the new Digimon you just created. Go to the save menu, and save the game with the second Digimon only in another save slot. Now shut off your game, and reboot with both Digimon again. Your second Digimon should have the item, but your original Digimon won't lose it. This can be done as many times as you want.

Dorumon
Reach level 16 with Agumon.

Wargreymon
Successfully complete the Undead Yard quest with Agumon or the Item Road quest with Guilmon.

Unlockable Digivolutions
To unlock the following digivolutions, you need to reach level 16 and speak to the DigiLab attendant to unlock the Digivolve technique

Easy tech ups
After you have unlocked the "Fortress" in Death Valley, whenever you need to equip a new weapon that is too high in tech points, just return to the Fortress and fight up and down the tower multiple times. You will receive between 10 to 60 tech ups in one revolution.

Game Modes
Unlocking of game modes is applicable to the first player/team leader only. To unlock it for the other players (second to forth players), you must switch the first player with one of the other players.

Herculeskabuterimon
Successfully complete the Undead Yard quest with Guilmon or the Item Road quest with Agumon.

Weregarurumon
Successfully complete the Undead Yard quest with Dorumon or the Item Road quest with Veemon.

Unlocking Ultimate and Mega level digimon in Normal Mode
Most of these are done by completeing side quest. The rules for these side quest are given in the game and by completeing them you get a digivolution.

Defeating Aprokrimon
First, destroy the five spike balls on the posts around him, avoiding the fire shots and wind blow. Whenever five flying things come to attack, just block. Do not try to jump on the area that he is on, as you will get shocked. After the spike balls are destroyed, he will shoot a purple attack that follows you. You must run around trying to hit him without getting hit. Magic and a gun weapon work well; you do not have to walk up to him, but they do smaller damage. Physical attacks are more powerful, but you must risk getting close to him.